An allergy occurs when the immune system identifies a harmless substance as being foreign and produces antibodies to fight the substance. Any substance that causes this reaction is called an allergen.

In some cases, an allergic person can avoid contact with the allergen. However, when people become allergic to medications necessary for their health, avoidance may not be possible. Desensitization (immunotherapy) can help many patients to reduce or eliminate allergy symptoms.

Desensitization is the process of decreasing a patient’s sensitivity to an allergen. This is accomplished over time by injecting the patient with gradually increasing amounts of the allergen. When this process is targeted toward enabling patients to tolerate medications to which they are allergic, it is called drug desensitization therapy.

Not all reactions to medications are allergic. Some are simply side effects, which may be treated by adjusting the dosage of medications or by addressing uncomfortable or inconvenient symptoms. Desensitization will have no effect in these cases, and it is important to determine that a patient is in fact allergic to the medication before beginning drug desensitization therapy.

Drug desensitization is considered only when there is no alternative medication or therapy available to treat a condition. For example, a person with diabetes who becomes allergic to insulin or someone who develops an infection that is resistant to alternative antibiotics might qualify for desensitization.

The patient may continue to have allergic reactions to the drug while desensitization takes place. Antihistamines, corticosteroids, epinephrine or other medications may be given to the patient to suppress any allergic symptoms while the desensitization process is completed. 

Desensitization requires consultation with an allergy specialist (allergist/immunologist) to minimize any risks. It is also necessary to consider the specific allergies, circumstances and physiology of each individual patient. It is important for patients to discuss the particulars of their situation with the physician and determine if desensitization is appropriate for them.